From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 22 Nov 2004 14:48:22 -0800 (PST) From: Christoph Lameter Subject: Re: deferred rss update instead of sloppy rss In-Reply-To: <20041122144507.484a7627.akpm@osdl.org> Message-ID: References: <20041122141148.1e6ef125.akpm@osdl.org> <20041122144507.484a7627.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: hugh@veritas.com, torvalds@osdl.org, benh@kernel.crashing.org, nickpiggin@yahoo.com.au, linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: On Mon, 22 Nov 2004, Andrew Morton wrote: > > The page fault code only increments rss. For larger transactions that > > increase / decrease rss significantly the page_table_lock is taken and > > mm->rss is updated directly. So no > > gross inaccuracies can result. > > Sure. Take a million successive pagefaults and mm->rss is grossly > inaccurate. Hence my suggestion that it be spilled into mm->rss > periodically. It is spilled into mm->rss periodically. That is the whole point of the patch. The timer tick occurs every 1 ms. The maximum pagefault frequency that I have seen is 500000 faults /second. The max deviation is therefore less than 500 (could be greater if page table lock / mmap_sem always held when the tick occurs). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org